Astronomical phenomenon what is the reason for the aperture around the moon?

We sometimes see a colored aperture next to the moon, but for some reason, some people think that this phenomenon will appear around the moon because of the good weather. Is that really the case? Next, the constellation knowledge will answer your question. Let's look at the astronomical phenomenon and what is the reason for the aperture around the moon.

The aperture around the moon is called "halo", also called "wind circle". Moonlight is refracted by clouds, forming an aperture around the moon, which can be used as a sign of weather changes. Before the weather changes, we sometimes see one or more colored or white apertures around the sun or moon, and the sunlight and moonlight seem dim. What happened? We call this aperture around the sun or moon "solar halo", the aperture around the sun "solar halo" and the aperture around the moon "lunar halo", which is a strange meteorological phenomenon. The color of halo is generally infrared violet.

Lunar halo is a phenomenon that light is refracted by moonlight when it passes through ice crystals in clouds, and becomes a colorful halo with infrared purple inside. The appearance of solar halo or lunar halo often indicates that the weather will change to a certain extent. Generally, a solar halo indicates that it may rain, while more lunar halos indicate that there will be wind. So there is a folk proverb: "The sun is dizzy in the middle of the night and the moon is dizzy at noon."

When you feel dizzy, there is usually no wind and thin clouds (cirrus, cirrostratus or cirrocumulus) are floating in the sky. Cirrus, cirrostratus and cirrocumulus are mainly composed of ice crystals. If we want to know that light will be dizzy if it is refracted by ice crystals, we need to know what kind of clouds cirrus, cirrostratus and cirrocumulus are and the related weather conditions. Cirrus is a thin, white feather-like cloud, which usually appears in a sheet or narrow band with a high cloud base. Cirrus clouds often indicate the arrival of high-altitude cold air or low pressure, and there will be precipitation. There is a proverb that says "there are hook clouds in the sky and rain in the ground", which is a kind of hook cloud in cirrus clouds. Cirrocumulus, often white and thin clouds, like fluffy cotton and tiny fish scales, are sometimes easily confused with high-level clouds, but isolated clouds are generally smaller than high-level clouds. There is a saying that "it is crazy if it doesn't rain", and cirrocumulus is often the precursor of wind and rain. Cirrostratus is flaky or layered, and its thickness varies greatly. Sometimes it is very thin, so you have to be very careful to see it, and sometimes it is thick enough to cover the sun. Cirrostratus often foretells changes in the weather system. There is a saying that "the sun is dizzy and it rains in the middle of the night, and the moon is dizzy and windy at noon", but it doesn't always bring wind and rain.

How is the halo formed? Why is it ultraviolet red? The ice crystals in Cirrus, cirrostratus and cirrocumulus are mostly hexagonal prisms. When sunlight enters the atmosphere, ice crystals act like prisms. After two refractions, sunlight is dispersed into colored light in different directions. Because sunlight is composed of seven colors of light: red, orange, yellow, green, blue, indigo and violet, and because the refractive indexes of different colors of light are different (red light has the longest wavelength and the smallest refractive index, while violet light has the shortest wavelength and the largest refractive index, which is called dispersion), the deflection angles are different after being refracted by ice crystals, and the minimum deflection angle is about 22? In this way, the inner ultraviolet red color halo is formed. The refraction deflection angle of some light is not 22? But greater than 22? , so the light outside the halo is brighter than that inside the halo. But not all refracted rays can form halos. As we can see, many refracted rays cannot reach our eyes. In order to observe the halo phenomenon, the thickness of the crystal must be greater than the wavelength of light, and the arrangement position in the air should make the light produce the minimum deflection angle after being refracted by ice crystals, and at the same time, there should be enough ice crystals to produce enough refracted light. So not all cirrus clouds, cirrostratus and cirrocumulus can get dizzy.

When the proportion of sunlight is strong, people can see two or three colors; When the sun is weak, people can only see white. Because the moonlight is weak, the halo they see is often only white. The common halo is this kind of refraction halo, which can only be formed in ice crystal clouds, cirrus clouds, cirrostratus and cirrocumulus, but not in middle clouds.

The size of the halo depends on the attitude of the ice crystal. If the ice crystal (hexagonal cylinder) drops horizontally, people will see a halo of 22 when sunlight enters from one side of the ice crystal and leaves from the other side. If the ice crystal (hexagonal cylinder) falls vertically, people will see a big halo of 46. There are two situations in this situation. First of all, light does not enter from the side of the hexagonal cylinder, but from the top of the hexagonal cylinder. When it comes out from a certain surface, the light will also be refracted, but the minimum deflection angle of this refraction is 46 instead of 22. Secondly, when the light enters the bottom from the side of the hexagonal cylinder, a 46 halo will appear, so the halo people see is a 46 halo ring.

In southern Fujian, lunar halo is more common than solar halo. "Huai Nan Zi" wrote: "Yao got up at 10 o'clock, and all the plants and trees were withered, and Hou Yi was ordered to shoot back at 10 o'clock. In fact, "Ten Days" is not a myth, but a natural light phenomenon. There are many halos in the sky, as if there were many suns. This is not only the naive explanation of nature by the ancients, but also the product of fantasy and imagination.

The spectacle of multiple halos in the sky also exists in contemporary times, but it is relatively rare. It is reported that1October 3, 1985, five wonders appeared over Suihua City, Heilongjiang Province. 165438+ At 0: 00 a.m., the sun's disk is red with golden edges, dazzling. There is a colorful halo around the sun. Spread from both sides of the sun to the north, there are two fake suns shining with colorful brilliance. There is a big white semicircle halo connected with four fake suns, just like wearing five balls on a necklace. There are also two rainbows with convex faces facing the sun in the sky, which are colorful and spectacular. 1986 12 19 From 9: 00 a.m. to 10: 30 a.m., five bright spots appeared in the southeast of Xi 'an, as if there were five more suns.

The number, brightness and size of solar halos vary with the distribution of ice crystals in the sky.

For a long time, working people have summed up many proverbs about the phenomenon of solar halo and lunar halo in their struggle and life practice, such as: solar halo wind, lunar halo rain; Lunar halo wind; There is no door under the moon, and it rains in the middle of the night; The bright moon has long hair, and it rains in the Ming Dynasty; The moon holds an umbrella, but it is better than three, and so on. It can be seen that the halo is related to the weather system, and its appearance is a sign that the weather will change. When we understand the optical meteorological principle of halo, we can use the rich experience of working people to see the sky and understand the meaning of weather proverbs, and at the same time summarize and improve them in practice, and we can get better results. Of course, forecasting weather changes depends on the development of clouds and other weather factors.

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